Digital systems, such as data processing systems, generally include a secondary storage facility used in conjunction with the data processing unit for the storage and retrieval of data.
Typical secondary storage facilities include direct access memory devices, such as magnetic disks, tapes or drum memories, and newer magnetic bubble memories. All of these devices have a common function, that is, to store data and be capable of retrieving accurately that data for use by the central processing unit. In particular, magnetic disk memories have become the main stay of secondary storage facilities for digital systems and have increased in complexity, density of stored data, performance capabilities and price performance.
The magnetic disk memory system comprises typically a disk drive, including the spindle, motor assembly and means for coupling a magnetic disk cartridge (hereinafter a "disk"), to the spindle for rotation about the spindle axis and magnetic Read/Write head means (hereinafter "heads") for Writing and Reading data onto and off of the magnetic disk. The drive further includes or is coupled to a disk controller, which performs operations in conjunction with or in response to the central processing unit for accessing the drive, positioning the heads, Reading and Writing the data and other functions known in the art with regard to the data and processing thereof.
In general, there are various sizes of drives, presently small 51/4" disks to the large 14" disk, as well as hard and floppy disk media. However, the drives are of generally two types: fixed disk, that is, fixed to the drive or not removable therefrom and removable disk cartridges. The removable disks may be either hard or floppy disks.
With respect to removable disks, a common problem associated with the disk is the interface between the disk hub and the drive spindle assembly along the axis of rotation/symmetry (hereinafter "axis of rotation"). In particular, the mating between the disk hub and the spindle must be accomplished in a relatively accurate, simple manner. It is desirous to position the disk hub on or matingly with the spindle and along the axis of rotation to effect accurate positioning of the head with respect to the disk. Also, accurate alignment of the disk along the spindle's rotational axis is desired such that the axis of rotation of the disk is aligned with the axis of rotation of the spindle. Any offset of the axis of rotation of the disk with respect to the axis of rotation of the spindle is commonly associated with the phenomena called "runout". The runout phenomena is a situation in which the circumferential tracks about the magnetic disk, formed by the head, as the disk rotates, are eccentric, that is, not the expected circular track. The eccentric tracks are difficult to follow during the Read operation, which affects the effective operation of the drive.
Prior art systems for mounting a removable disk, or a plurality thereof, have included means for loading or mounting the disks and to adjust for runout. One such prior art system for a disk 10 is shown in FIG. 1. As shown in FIG. 1, a spindle 12, having an axis of rotation 14, and coupled to the disk drive motor (not shown) for rotation, includes a radially extended surface member 16 fixedly attached to the spindle. The surface member 16 includes a raised surface, or ring member 18, at its outer diameter. The spindle 12 further includes a central conical member 20 for mating attachment to the disk 10, as later described. The spindle 12 further includes a ring magnet 22 used to magnetically attract the disk 10 and to hold it in attachment to the spindle. Generally, the magnet 22 is of sufficient magnetic force to transmit the torque from the rotated spindle to the disk. The disk 10 includes a hub 24, to which the disk cartridge, or platter 26, is attached by a clamp 27. In addition, the hub 24 mates with the spindle 12 to transmit the rotation of the spindle to the platter 26. The hub 24 includes a corresponding mating attaching conical portion 28 to couple to the spindle conical member 20. Because of mating problems associated with conical members and other sections, the hub further includes a flexible member, or diaphragm 30, extending radially from the conical portion 28 and terminating in a ring 32, having a surface 34, for seating on the flat surfaces of the ring member 18.
In operation, the disk hub assembly is mounted onto the spindle and the conical portions 20 and 28 of the spindle and hub respectively matingly contact at a point predetermined within certain accuracy along the conical portion 20. As the hub 24 approaches the spindle, the ring magnet 22 exerts a force on the hub ring 32 and attracts the hub ring 32 into contact with the ring member 18 of the spindle. Because both the spindle and the hub in this type of prior art system must be accurately machined, both along the ring member surfaces, a relatively easy and not excessively costly problem, but also, along the conical positions, a considerably more difficult and costly procedure, there is a substantial cost in this type of alignment system. In addition, as it is extremely difficult and generally impractical to accurately machine and mating conical portions 20 and 28 of the spindle and hub, respectively, and the mating portions 18 and 32 of the spindle and hub rings, respectively, such that all respective portions contact at predetermined locations, the attraction of ring magnet 22 on the hub 22 causes a flexure of the flexible diaphragm 30 in order that the hub mates with the spindle. Flexure in this system, however, leads to various runout problems. The difficulty in machining the conical portions in a mating fashion creates offsets in the axis of rotation of both the spindle and the hub such that a runout can be expected. In addition, the ring portions of the hub and spindle may contact in a skewed or offset orientation from the axis of symmetry. As the ring magnet is of sufficient magnetic strength/capability to transmit the torque to the hub disk assembly, the magnetic attraction force of the magnet could attract the nearest ring portion of the hub in contact with the ring of the spindle angularly skewing the hub to the spindle. This situation would angularly position the conical portion of the hub onto the spindle conical portion relative to the axis of rotation. Accordingly, various runout problems are encountered with this type of system, resulting in eccentric tracks, that is, eccentric tracks are Written and Read onto the disk and off the disk by the Read/Write heads. Moreover, when the disk is removed and then reinserted onto the same spindle, or onto another spindle, the skew or offset resulting in the first set of runout conditions generally changes. When a new runout occurs with different offsets, the tracks which the heads are attempting to Read and Write upon, are not aligned with the original eccentric tracks of the previous spindle. In this manner, the Read/Write heads of disk drives have considerable difficulty in following the tracks. As such, the Read/Write heads require expensive, sophisticated servo techniques for adjusting the heads with respect to the tracks.
Accordingly, it is desirous to have a spindle/hub assembly which will accurately and repeatedly mate with one another such that runout is minimized, or is effectively eliminated. It is further desirous to have a hub spindle assembly which is not affected by removal and reinsertion into a particular spindle, or any similar spindles, but which will present the same tracks to the heads. In addition, it is desirous to have the tracks Written by the heads in a circular manner with respect to the axis of rotation/symmetry of the spindle in all cases of spindle/hub assembly. In this manner, hub interchangeability is accomplished, track following is ensured, and runout with respect to the axis of rotation, or with respect to the heads, is essentially eliminated.